Audio mixers (also referred to simply as “mixers”) are constructed basically in such a manner that signal processing, such as control of various characteristics and level adjustment, are performed, in individual ones of a plurality of channels, on audio signals supplied from external sound sources via an input (having a plurality of jacks) of the mixer, the thus-processed audio signals are mixed by means of buses of a main output route, the thus-mixed audio signal are processed by means of output channels and then the thus-processed audio signals are output to the main output (having a plurality of jacks). To the main output are connected main speakers for amplifying the audio signals and audibly outputting the amplified audio signals to the venue, wedge speakers for audibly outputting the audio signals to human players (or human performers), etc. A user (i.e., human operator of the mixer) sets, for each of a plurality of input channels, send gains to the buses (i.e., gains of audio signals to be sent to the buses) so that a mixing ratio of the audio signals in the mixed audio signal of each of the buses can be adjusted. The gain is a value in decibels, and the gain in positive value indicates amplification of the audio signal while the gain in negative value indicates attenuation of the audio signal.
In the conventionally-known mixers, a “CUE” function has been known which, for permitting user's test-listening, outputs an audio signal of a desired channel, selected as an object of test-listening, from a monitor output different from a main output without affecting an audio signal of an main output route. User's headphones etc. are connected to the monitor output. According to the disclosure in Japanese Patent No. 4003639, a send gain to a monitor bus for test-listening is set separately from a send gain to a bus of a main output route, a plurality of audio signals are mixed in the monitor bus, and the resultant mixed audio signal is output via a monitor output.
With the conventionally-known cue function, however, it is not possible to adjust a parameter of a currently test-listened-to audio signal without affecting an audio signal of the main output route. But, with a conventionally-known preview function of a mixer, a user can adjust a signal processing parameter of a desired audio signal, selected as an object of test-listening, without affecting an audio signal of the main output while listening to an audio signal of the monitor output. Japanese Patent Application Laid-open Publication No. 2016-181833 discloses, as an example of the preview function, that a temporary channel is created, in response to a preview start instruction of a given input channel, for a monitor output purpose such that the same audio signal as supplied to the given input channel is supplied to the thus-created temporary channel, and that a value of a parameter of signal processing (signal processing parameter) of the given input channel is copied to the temporary channel so that the parameter of the signal processing to be performed on the supplied audio signal is adjusted in the temporary channel. Further, Japanese Patent Application Laid-open Publication No. 2016-178391 discloses that a non-temporary cue output channel is provided for a monitor output purpose such that, in response to a preview start instruction of a given output channel, the same audio signal as supplied to the given output channel is supplied to the thus-created cue output channel, and that a value of a parameter of signal processing of the given output channel is copied to the cue output channel so that the parameter of the signal processing to be performed on the supplied audio signals can be adjusted in the cue output channel in response to a user's operation.
Furthermore, Japanese Patent No. 4066254 discloses a method for readily setting a value of a send gain from each of input channels to a bus for a wedge speaker in a conventional speaker, which particularly discloses a technique for, in response to a user's instruction, copying a value of a send gain from each of the input channels to a bus for a main speaker as a send gain from that input channel to the wedge speaker.
However, with the conventionally-known preview function, in previewing a mixed audio signal of a given output channel selected as an object-of previewing (object-of-previewing output channel), it is not possible for a user to adjust a mixing ratio of a plurality of audio signals in the mixed audio signal of the object-of-previewing output channel without affecting an audio signal of a main output.